Field of the Disclosure
The present application relates to an organic light emitting device, and more particularly to a white organic light emitting device adapted to enhance efficiency and color reproduction range and reduce power consumption.
Description of the Related Art
Nowadays, a display field for visually representing an electrical information signal has been rapidly developed with the spread of substantial information society. In accordance therewith, a variety of flat panel display devices with features, such as slimness, light weight and low power consumption have been developed. Also, the flat panel display devices have been rapidly replacing the existing cathode ray tubes (CRTs).
As examples of the flat panel display devices, liquid crystal display (LCD) devices, plasma display panel device (PDPs), field emission display (FED) devices, organic light emitting display (OLED) devices and so on can be introduced. Among the flat panel display devices, the OLED device is being considered as the most competitive application. This results from the fact that the OLED device without any separated light source can compact its applied appliance and display vivid colors.
It is necessary for the OLED device to form an organic light emission layer. The organic light emission layer is formed using a deposition method of the related art which employs a shadow mask.
However, a large-sized shadow mask can be sagged due to its load (or its weight). Due to this, a fault can be generated the formed organic light emission layer pattern. Also, the shadow mask cannot be used several times. In view of this point, it is necessary to provide alternative proposals.
As one of several methods for removing the shadow mask, a white OLED device has been proposed. The white OLED device will now be described.
The white OLED device enables a plurality of layers between an anode and a cathode to be deposited without any mask at the formation of a light emitting diode. In other words, an organic light emission layer and the other organic films, which include different materials, are sequentially deposited in a vacuum state. Such a white OLED device is used for various purposes, such as a thin light source, a backlight of the LCD device, a full-color display device with color filters or others.
The ordinary white OLED device uses a phosphorescent/fluorescent stack structure. The phosphorescent/fluorescent stack structure includes a first stack using a light emission layer of a blue fluorescent material and a second stack which is formed on the first stack and uses another light emission layer of a yellow-green phosphorescent material. Such a white OLED device can realize white light by mixing blue light emitted from the blue fluorescent mater and yellow light (or yellow and green lights) emitted from the yellow-green phosphorescent material.
However, it is necessary (or difficult) for the white OLED device of the phosphorescent/fluorescent stack structure to enhance luminous efficiency and color reproduction range and reduce power consumption.